Same sounds and styles, for the most part.
3k:
speakers, Smart media card, USB in and out hubs, very small and lightweight, MUCH cheaper
Ty:
separate outs, 3rd RH sound, hard drive option, better key feel(although both are kinda flimsy compared to older stuff)more Foot swith options.

The Tyros is a larger piece with lots of wasted space on the sides. The 3k is more compact. As far as I know, the mega sounds and styles all swith between the 2 with no drawbacks too.